The use of thermoplastic bags for a number of household and industrial uses has gained wide acceptance. Many of these bags are constructed from a simple structure having two layers of thermoplastic film which are joined along three sides and having a mouth opening formed along the fourth side. This basic structure has been adapted to a wide range of sizes and configurations that vary with the intended end use of the bag. Advancements in resin technology have enabled manufacturers to produce bags of ever increasing strength, puncture resistance, and resistance to tear while downgaging the film used to make the bags. The end result has been a significant savings in material costs and improvement in the quality of the product made available to the consumer.
The present invention is concerned with addressing some of the problems encountered with bags intended primarily for holding garbage or yard waste. However, it may be adapted for use in grocery stores to hold fresh produce or bulk foods. Both these types of bags have been provided in the form of a collapsed, continuous roll of bags. The bags on the roll are separated by perforations so that a consumer can unwind and tear off individual bags from the roll. These bags have also been sold in non roll form wherein individual bags are separated and folded. In either case downgaging the bag film has made it difficult for consumers to open the bag mouth because the very thin film layers tend to adhere to each other. Another problem has developed from the advancements in perforation technology that permit consumers to sever bags very cleanly from a roll of bags. The separation can be so neat that consumers often frustrate themselves attempting to open the bottom sealed end of the bag. That bottom end often closely resembles the top open mouth end of the bag. Customer perception of the bag is often negatively affected by the difficulties encountered locating the top of the bag and then separating the bag film layers for filling.
Garbage bags may be provided with a means to close the bag securely after loading. Typically such bags are provided with a separate closure means in the form of a plastic or metal tie device. Such devices are well known and require that the neck of the bag be bunched together by the user. This approach has the disadvantage of requiring that a number of small closures be inventoried and tracked by the user. Also, this type closure results in the loss of some amount of useable bag volume to the need to gather the neck of the bag for tying off.
U.S. Pat. No. 3,979,050 to Cilia which discloses a multiply plastic film bag comprising a first ply of flat flexible plastic superimposed over a second ply of flat flexible plastic film. At least a portion of the first ply of film defining the openable end of the bag is distorted to separate at least a portion of the confronting face of the first ply of film from the opposed confronting second ply of film. The distorted portion of the first ply of film provides means for separating the confronting faces of the first and second plies of film. Heat may be used to distort the first ply in order to create the separation between plies. This distortion would be difficult to control during actual manufacture of the film. Moreover, heat shrinkable film is required, and this requirement places a substantial limitation on the range of materials that can be used to make the bag.
U.S. Pat. No. 5,246,110 to Greyvenstein discloses a refuse bag joined at three sides and an open fourth side which includes projecting tie parts that can readily be tied by hand. The tie parts are rounded peaks separated by convex valleys. Each peak has side portions and a top which has a convex part including convex transitional portions connected to the side portions which otherwise connect to the valleys. Preferably the peaks and valleys form a sinusoid. This design is disadvantaged by the tendency of the tie parts to be welded together by the cutting action forming them. This cut welding inhibits the opening of the bag. The handles of this bag are in exact alignment when the bag is in lay flat condition.
U.S. Pat. No. 4,890,736 also to Greyvenstein discloses a roll of thermoplastic material from which is formed a plurality of refuse bags. Pairs of heat seals are formed transverse to the direction of the bag at about bag length distances apart. The heat seals are separated by perforations. Every embodiment of the bag requires the formation of a transverse, wave-like cut between the pairs of heat seals resulting in the formation of four cut-outs and four projecting tie parts.
U.S. Pat. No. 5,215,275 to Gold describes a process for making a roll of plastic bags. The bags are made from a two-ply web sealed along its edges. Essentially non-coincident perforations are made in the top edges of each bag. The perforation in the first ply is straight and the perforation in the second ply is curved. It is disclosed that the non alignment of the perforations makes the bag easy to open.
U.S. Pat. No. 4,125,220 to Suominen discloses a plastic shopping bag having a reinforced handle. The handle has a symmetrical wave configuration and is reinforces by a pair of reinforcing strips glued to either side of the collapsed tube of material from which the bag is made. After attachment of the reinforcing strips, a cutter cuts through every layer of bag material along a sinusoidal path.